To Bake the Cake
- Set the rack in the middle level inside the oven and then preheat the oven to 180°C. Line a cake pan with baking paper.
- Boil 2 tbsp of water and add 2 tbsp of hazelnut flavoured instant coffee over medium-low heat. Stir until concentrated coffee is formed.
- Add dark chocolate, vegetable oil, and unsalted butter and stir well until the mixture is smooth and well combined. Remove the pot from the heat and reserve.
- Sift cake flour, salt, baking soda, and baking powder into a large mixing bowl.
- Add sugar into the mixing bowl and mix well using a whisk.
- In another bowl, mix eggs, plain yoghurt and vanilla extract. Mix well using the whisk.
- Combine the coffee-chocolate mixture and the flour mixture together. Stir well using a spatula until the flour is just combined.
- Add the egg mixture and continue mixing using the spatula and/or whisk until the batter is smooth.
- Pour the batter into the prepared baking pan and bake for 18 mins.
- Test with a toothpick to check if the mocha cake is cooked. If the flour is still not done, bake for a further 5 mins more. If the flour is well cooked, leave it to cool down while making the toffee and nut topping.
To Make the Toffee and Nut Topping
- Sift caster sugar, salt, and flour into a mixing bowl. Set aside.
- Add evaporated milk and hazelnut coffee into a saucepan and bring to a boil over low heat. Stir until they are well mixed.
- Add butter. Continually stir until the butter is melted.
- After the butter is completely melted, increase the heat to medium-low, add the reserved flour mixture into the pot and continually stir while adding the mixture.
- Remove the pot from heat when the topping boils and then add the chopped nuts.
- Pour the nuts topping over the mocha cake. Using the spatula to spread the topping all over the cake evenly.
- Switch oven to grill setting at 180°C (do not place the cake too close to the element) and grill for 10 minutes until the topping caramelises.
- Remove from the oven and allow the toffee cake to cool down.
- Transfer to a wire rack to cool completely.
- Use a sharp knife to cut the cake. Serve.